Dog and cat age in human years
Two ways vets compare ages, side by side — and what the stage means for care.
Two ways to count
The familiar rule: a dog’s first year equals about 15 human years, the second about nine more, and each year after that four to seven, depending on size — big dogs age faster. Cats follow the same first two years, then about four a year.
In 2020, researchers compared DNA methylation in dogs and people and proposed human age ≈ 16 × ln(dog age) + 31. It was built on Labradors, so it is most reliable for medium-to-large dogs over a year old.
Tailwise is for general information and is reviewed by veterinary professionals, but it is not a substitute for advice from your own vet, who knows your pet. How we check facts